One of the rarest materials in the world was created in merged dune sand, which an electrical discharge had heated to more than 1700 degrees Celsius. There was a quasi stall - a fabric in which the atoms obey the principle of order as in a crystal, but do not repeat themselves strictly. There is only one hand full of natural - or at least outside the laboratory - examples of such quasi ristals. As a working group around the geoscientist Luca Bindi from the Università Di Firenze reports, she discovered another example of this exotic fabric class in a region in the United States. According to its publication in the specialist magazine "PNAS", the only a few micrometer in the wall of a fulgurite was created - a tube made of baked and merged sand, which is generated by extremely strong currents such as a lightning strike.
While normal crystals consist of nuclear groups that can be lined up to the end of the infinity, the nuclear groups of the quasi -ristal are ordered in themselves as in a crystal, but they cannot be arranged as regularly because of their special symmetry properties. Quasikristalls are so rare because atoms prefer to arrange crystals in the form of "real" - or simply do not adhere to any special order. Only in special circumstances, for example extreme pressure or temperature conditions, the regular structures of the quasi ristals also form. For example, one of these exotic minerals was found in a meteorite, another was created during a nuclear explosion.
However, the quasicrystal discovered by Bindi and his team is an exotic even among his peers. Most of the quasicrystals known to date have a five-fold symmetry, while the substance found in the dune with the molecular formula Mn72,3si15,6Cr9,7al1,8NI0,6 has an unusual twelve-fold symmetry. In addition, its chemical composition suggests that its origin is not completely natural. As the team around Bindi reports, the molten sand contains traces of metal. This comes from a nearby power line, which was allegedly destroyed in the same storm that also caused the lightning to strike the dune. The metals manganese, chromium, aluminum and nickel contained in the quasi-crystal probably originate from a molten fragment of the power line. Only silicon comes from the quartz of the sand grains. In fact, the working group cannot say for sure whether it was really lightning that caused the melting tube to form in the sand – or whether it was possibly the power line itself that triggered the discharge.
